Specific Aims: 1. The Role of Pili in the Host-Parasite Relationship. a. Characterization of the Mammalian Receptor of Gonococcal Pili. b. Species and Organ Distribution of the Pilus Receptor. 2. Characterization of Major Outer Membrane and Opacity Proteins. a. Immunological and Chemical Relationships of the Serotypically Specific Major Outer Membrane Protein and the Opacity Proteins. b. Determination of the Amino Acid Sequence of a Gonococcal Major Outer Membrane Protein. c. Studies Concering the Function of the Major Outer Membrane Proteins. 3. Further Studies on Gonoccal IgAl Protease.